Short term rentals in LA, is it legal?

I am getting conflicting information online about whether or not it is legal to do AirBNB in LA county, so I thought I would ask you guys. We have recently purchased a fourplex, where two of the units have long term renters, we intend to move into the third, and was considering doing Airbnb on the fourth one. Is this legal under current legislation? 

Thank you for any input.